"We synthesize unique nanoscale building blocks and stack them into interesting structures. In this case, we were able to stabilize these theorized transitional structures and demonstrate important quantum optical properties."
— Ou Chen, associate professor at Brown University
"Being able to observe these structures is a fundamental breakthrough in materials science, and it gives us greater control over nanomaterial engineering."
— Tim Moore, assistant research scientist at University of Michigan
A New Phase of Matter, Stabilized
Researchers from Brown University and the University of Michigan have achieved a long-sought milestone in materials science: they have stabilized a previously theoretical intermediate structural phase that exists between face-centered cubic (FCC) and body-centered cubic (BCC) arrangements.
The breakthrough centers on a new type of nanoparticle superlattice, built from truncated octahedral silver nanoparticles nicknamed "mecons." Coated with sticky molecules, these mecons self-assembled into the novel structure.
Key Findings
- The New Structure: The team successfully created a nanoparticle superlattice that matches the elusive intermediate phase predicted by the Nishiyama-Wassermann pathway—a structural transition long theorized but never before observed in a stable form.
- Quantum Optical Properties: The resulting superlattice exhibits deep-strong light-matter coupling at room temperature, a property that could have significant applications in quantum computing and quantum sensing.
Background: From Theory to Reality
FCC and BCC are two of the most common atomic arrangements in metals. Some metals transition between these structures when heated, but the intermediate phases predicted by the Nishiyama-Wassermann pathway have historically been too unstable to observe directly.
The key to this breakthrough was the precise control of the building blocks. The researchers synthesized mecon-shaped silver nanoparticles with varying degrees of roundness, then allowed them to self-assemble. Computer simulations confirmed that the resulting structures matched the predicted transient states.
Implications & Next Steps
This work represents a fundamental breakthrough in materials science, demonstrating that theoretical structural phases can be engineered and stabilized at the nanoscale. The ability to control the assembly of nanoparticles into these exotic lattices opens new doors for designing materials with custom optical, electronic, and mechanical properties.
Funding
The research was supported by grants from the National Science Foundation and the Department of Energy.